Fix next_posts_link() for Custom Post type WordPress

<?php

$paged = ( get_query_var( 'paged' ) ) ? get_query_var('paged') : 1;
$args = array( 'post_type' => 'portfolio', 'posts_per_page' => 2, 'paged' => $paged );
$loop = new WP_Query( $args );
while( $loop->have_posts() ) : $loop->the_post();

the_title();
the_content();

endwhile;

next_posts_link('&larr; Next', $loop->max_num_pages);
previous_posts_link('Previous &rarr;', $loop->max_num_pages);

?>


//Fix previous_posts_link() And next_posts_link() For Custom Post Types